TRW Power Steering Pump Catalog & Steering Gear Adjustment Screw: 6 Questions from a Parts Buyer

Every few months, the same questions about TRW steering hardware cross my desk: Where is the current pump catalog? What does the adjustment screw really do? And why is my repair estimate all over the place?

I am the procurement manager at a mid-size automotive metal-forming company in Michigan. For the past eight years I have managed our repair and maintenance budget—roughly $220,000 a year, maybe $210,000, I'd have to check—and negotiated with more than 60 vendors. I am not an engineer, so this is not a factory training manual; it is what I have learned from purchase orders, warranty claims, and a few mistakes with a dollar sign attached.

1. Where can I find a TRW power steering pump catalog?

Start with ZF Aftermarket (aftermarket.zf.com), not an old trw.com catalog. According to ZF's official company history at zf.com, ZF completed its acquisition of TRW Automotive in May 2015, and the TRW steering product line is now part of ZF's aftermarket portfolio. The current interactive catalog is the practical replacement for the older printed TRW power steering pump catalog; searching by vehicle or by the old OE number usually leads to the current replacement part.

My purchasing rule is simple: if a TRW power steering pump catalog search shows a part number but no OE cross-reference, call before ordering. The same pump family can have different flow ratings or pressure settings, and the only visible difference might be the pulley size or a stamped marking. Restocking fees are how I learned that one (note to self: compare the old part against the listed part before approving a substitute).

2. What is the TRW steering gear adjustment screw?

On many TRW steering gears—especially the recirculating-ball boxes used in trucks and SUVs—the adjustment screw sits under a locknut on the gear housing. It moves the sector shaft slightly toward the ball nut, which takes slack out of the straight-ahead position. Some play is normal, which is why tighten it until it feels right is not a procedure. Factory service manuals call for a rotating-torque check expressed in inch-pounds, not feel.

I don't have hard data on how many gearboxes fail because of over-adjustment, but anecdotally I have seen a TRW steering gear adjustment screw tightened just enough to make a worn gear feel better. The problem is that the wear is still there. If you are doing this job yourself, use the vehicle-specific manual, back off the locknut slowly, and do not turn the screw beyond the service spec. A quarter of a turn is more significant than it looks.

3. New, remanufactured, or aftermarket pump: which is the real bargain?

In 2024, I went back and forth on a pump decision for a delivery van. A remanufactured unit cost roughly 40% less than a new pump, and the remanufacturer had a solid warranty. But once I added freight, core handling, and the likely cost of a second repair visit if the unit failed, the savings narrowed quickly. For the van that runs daily, we chose new. For a spare parts truck that sits most of the week, I might have chosen differently.

That is the total-cost-of-ownership habit I have built by tracking invoices for years. The right answer depends on your shop volume, vehicle value, and tolerance for downtime. Whatever you pick, new or reman, make sure the pump specification matches what the TRW catalog says. I once assumed same fitment meant the same pump. It did not, and the second labor charge was on me.

4. Does it matter that ZF now owns the TRW brand?

Yes, mainly for part-number research. TRW Automotive went through different owners over the years, and ZF formally completed its acquisition in May 2015. The TRW name remains in the aftermarket range, especially for steering and suspension, but many older TRW numbers have been superseded by ZF Aftermarket part numbers. If you are maintaining price books or sourcing BOMs, check for supersession instead of ordering from a catalog page that is years out of date.

It also matters for warranty claims. Keep the invoice and the catalog part number together. When a supplier asks whether the pump is an original TRW/ZF unit or another brand, that is not small talk; it determines how a claim gets processed. Part number mismatches are the most common reason a credit request gets delayed in our cost tracking system.

5. Why do two estimates for the same steering work look so different?

Usually because the scope is different, not because one shop is greedy. I have reviewed quotes side by side for our work van. The lower estimate was based on a remanufactured gear and did not include alignment; the higher estimate included a new TRW gear from the ZF Aftermarket catalog, fresh hardware, a fluid flush, and alignment. Different products and different outcomes translate into different prices.

Specialization matters too. We have used Muffler Man Westland when a fleet truck needs exhaust work; a specialist who does one job well may not be the right choice for a different job. It is the same with steering: ask what parts will be installed and whether the shop performs that kind of repair regularly, then compare the scope line by line instead of just the bottom number.

6. Should I replace rear differential fluid while the steering is being fixed?

Rear differential fluid has nothing to do with a steering pump or gearbox, so do not let a shop bundle them artificially. But if the truck is already on a lift for steering work, it is a smart time to check the rear axle service history. On many trucks and SUVs, replacing rear differential fluid is easy to forget because the differential has no dipstick and the service interval is measured in miles, not months.

Follow the factory maintenance schedule and use the exact fluid type listed in the owner's manual, including limited-slip additive if the axle requires it. We track rear diff service in the same spreadsheet as engine oil, and that habit has saved us from at least one expensive axle repair. If the vehicle is new to you and the history is unknown, replacing rear differential fluid is cheap insurance compared with a differential rebuild.

Context matters, of course. A light-duty vehicle that never tows is different from a work truck that carries heavy loads every week. I can only tell you what works for our 12-vehicle fleet in Michigan; if you tow heavy loads or drive off-road regularly, follow the severe-service schedule in the manual instead.